DefenseTech reports that they're exploring the possibility:

The White House has completed yet another piece of its never-ending review of the Clinton-era 1996 National Space Policy.

U.S. SPACE-BASED POSITIONING, NAVIGATION, AND TIMING POLICY, signed by the President on 8 December 2004, "establishes guidance and implementation actions for space-based positioning, navigation, and timing programs, augmentations, and activities for U.S. national and homeland security, civil, scientific, and commercial purposes."

In other words its a GPS policy, and pretty aggressive one at that.

The policy, which also comes in a classified flavor, reportedly resulted in a directive to the Secretary of Defense (SecDef) to develop plans to shut down civil use of U.S. GPS signals in certain emergencies and to deny adversaries access to foreign space-based satellite navigation services, such as the European Union's Galileo system.

(This last bit quite understandably has the Europeans upset.)

If they discuss this with anyone with half a brain who doesn't live in a cage in the White House basement, I suspect what they'll discover is that the genie is out of the bottle and there is no going back: that large parts of out "Homeland Security" apparatus use civilian GPSs, which I expect are much cheaper and more plentiful than their military counterparts; and that disabling "civilian" access to the GPS data would be a Homeland Security disaster.

I guess the real question is not whether it is feasible to turn off civilian access, but whether this administration listens to anyone but their own caged "experts."

(They do throw some language around like without unduly disrupting blah blah blah, but I don't see how they can deny use of GPS systems to adversaries any more than they can deny them use of the Internet without major service interruption; the passage with the cushioning language reads not so much like a piece of coherent policy as like a hostile compromise between common sense and stark raving lunacy.)

UPDATE: Here's the AP version of the story. And the UK's Inquirer discusses it as a form of trade war: Galileo versus GPS: A trade war in the making:

According to the anonymous source, President Bush has responded by instructing the US Department of Defense to develop plans to disable an enemy's access to the US navigational satellites and to similar systems operated by others "in certain areas". This is clearly aimed at Galileo.

Although such action "would come under only the most remarkable circumstances", it's a clear threat. Of course Europe can claim that Galileo has no military applications until it is blue in the face. But Bush has merely found another axis of all evil - anyone who puts a satellite into space. Gosh, doesn't that conveniently include the French?

And in a dizzying bit of spin, the NRO's Carlos Ramos-Mrosovsky uses the Galileo system as an example to illustrate his thesis that the " European Union is held together by nothing more than anti-Americanism."